The objective of this SBIR Phase I project is to develop a novel sequence-specific capture (SSC) technology to quantitatively and robustly retrieve circulating miRNAs from blood, which can transform the utility of circulating miRNAs testing in diagnosis of diseases including cancer and cardiovascular disease. Circulating miRNAs have emerged as novel biomarkers for many diseases. To date, however, there are no miRNA-based assays that can be used clinically. This is because miRNA-based assay is based on quantification of miRNA biomarkers and current assays are unable to accurately determine levels of circulating miRNAs. One major reason for this is the lack of methods that can quantitatively retrieve circulating miRNAs in a robust manner. The most commonly used method (silica-based extraction) for retrieving miRNAs is based on adsorption of polar molecules on polar silica and was developed to extract large DNA or RNA fragments. Because miRNAs are so small, their interaction with silica is much weaker than that of large fragments with silica. Ths means that miRNA adsorption on silica can be easily interrupted by other molecules in blood. Clearly, weak adsorption of miRNAs on silica is an inherent problem that cannot be easily solved for quantitatively retrieving circulating miRNAs. Recently, we have developed a novel SSC method by incorporating two breakthrough technologies invented by us, and successfully used it to quantitatively retrieve DNA from stool and blood in a robust manner. Unlike silica-based extraction whose performance deteriorates with a decrease of the size of DNA or RNA, the recovery and robustness of SSC actually increase with a decrease of the size of DNA or RNA. Considering the fact that we have demonstrated that our SSC method could quantitatively and robustly retrieve circulating DNA and that circulating miRNAs are much shorter than circulating DNA, we expect that our SSC technology should work for quantitatively and robustly retrieving circulating miRNAs from blood as well. Therefore, we propose this SBIR project to develop our SSC method for quantitatively retrieving miRNAs from blood. Clearly, success of this project will have a great impact on human healthcare, for it can provide a method for quantitatively retrieving circulating miRNAs, hence transforming the utility of circulating miRNA- based assays in disease diagnosis.